How to solve "INS-32035: The chosen installation conflicts with software already installed in the given oracle home" when installing into an old directory

Workaround for the error

INS-32035: The chosen installation conflicts with software already installed in the given oracle home

from the Oracle Universal Installer:

1. detatch the home from the ORACLE_HOME you install from:

cd $current_oracle_home/oui/bin
./runInstaller -detachHome ORACLE_HOME=/u01/oracle/product/11204 invPtrLoc=/u01/oracle/product/11201/oraInst.loc

2. edit the file /u01/oraInventory/ContentsXML/inventory.xml

In my case from:

<HOME_LIST>
<HOME NAME="OraDb11g_home1" LOC="/u01/oracle/product/db/11201" TYPE="O" IDX="1"/>
<HOME NAME="OraDb11g_home2" LOC="/u01/oracle/product/db/11204" TYPE="O" IDX="2"/>
</HOME_LIST>

to

<HOME_LIST>
<HOME NAME="OraDB11g_home1" LOC="/u01/oracle/product/db/11201" TYPE="O" IDX="1"/>
</HOME_LIST> 

3. Delete the files in /u01/oracle/product/db/11204 physically from disk, before you try again.

That's it.
Universal Installer should now recognize the selected directory, and not give you any complaints when reinstalling into the same directory.